Ever increasing needs of the urban population in public vehicles can be satisfied only provided that the level of specialization of production of corresponding vehicles in high, said level allowing mechanization and automation of the production process to be carried out on a wide scale. The required level of specialization of the production processes is in turn inseparable from the high degree of unification of sub-assemblies and parts of these vehicles.
Meanwhile, at present the designs of vehicles even within one kind of transport are unnecessarily various.
In particular, the Soviet industry puts on the market a series of motor buses having different lengths and passengers (load-carrying) capacity, consisting of motor buses of an original single-unit structure based on chassis units of trucks.
Bodies of these motor buses are unified practically only in terms of used (starting) materials and some assemblies of interior equipment. This fact results in a very low level of unification of such a series, said level being of about 10%.
Known in the art is a series of motor buses differing in their lengths and capacities and provided with bodies comprising unified front and rear end face portions (elements, doors, windows, and body panels of several standard sizes, and interior equipment ("Lastauto-Omnibus", FRG, 1974, No. 10, pp. 44-47). The level of unification of the buses of the above series reaches 25 to 30%.
A further step to increasing the level of unification of the standard size series of vehicles consists in the provision of said vehicles assembled from the module elements.
Known in the art is a module element of a city motor bus or similar vehicle, e.g. trolley bus, which is a transverse window section of the body, open at the end portions, each of the side walls of said section being provided with a window (U.S. Pat. No. 3,794,374).
In a motor bus assembled from such module elements, the parts and assemblies of the body are unified practically completely, the module elements of said body being joined end to end and disposed between front and rear elements which are also unified within the limits of the standard size series (Carl A. Gottesman, Avtobus contserna GMC printsipialno novoi construktsii, "Avtomobilnaya promyshlennost SShA", 1975 No. 8, pp. 5-6, FIG. 2). Such design makes it possible to assemble bodies of different lengths in the same assembly jig and to widely apply automatic welding.
The level of unification of the buses of standard size series having the above described module structure of the body is of 40 to 45%.
However, the principle of assemblying buses from separate modules, which is applied only to the body design as above described, practically takes into consideration only one parameter varying within the series, i.e. the bus length. Meanwhile, the bus length is associated with many other parameters, particularly load-carrying capacity (passengers capacity).
In accordance with the existing practice of bus construction, to obtain a bus of a certain standard size, the body assembled from a required number of module elements is mounted on a chassis of a corresponding load-carrying capacity. Since as a rule the chassis of all the buses constituting the standard size series are made in accordance with the biaxial layout, the carrying capacity of the wheel pair is variable within the limits of the series. This fact determines design differences among the chassis in the buses of different load-carrying capacities, and the difficulty of their unification within the standard size series of buses.
Obviously, the wide range of chassis restrains the increase in the capacity of the manufacture of buses, determines a high cost of their production and a wide range of spare parts which results in the complication of repair and operation.
Moreover, since the base distance of a wheel chassis varies with the change in the bus length, the dimension of a module element taken along this length should be multiple of the difference between the base distances of chassis of the neighboring buses in the standard size series. The above requirement causes the need of excessively fractional division of the bus into module elements to obtain an optimum distribution of load between the wheels. The above fractionality of dividing the body results in an increase in the number of module elements which fact, among other things, adversely affects the assembling productivity.